<template>
  <div class="spec-preview" @mousemove="mouseMove">
    <img :src="imgUrl" />
    <div class="event"></div>
    <div class="big">
      <img :src="imgUrl" ref="bigImg" />
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  props: ["skuDefaultImg"],
  mounted() {
    this.$bus.$on("getImgUrl", (imgUrl) => {
      this.imgUrl = imgUrl;
    });
  },
  watch: {
    skuDefaultImg(newval) {
      this.imgUrl = newval;
    },
  },
  data() {
    return {
      imgUrl: "",
    };
  },
  methods: {
    // 1.图片的放大镜效果
    mouseMove(e) {
      const oMask = this.$refs.mask;
      const oBigImg = this.$refs.bigImg;
      // 获取当前鼠标的位置
      let mouse = {
        x: e.offsetX,
        y: e.offsetY,
      };
      // 计算出mask宽高的一半
      let mask = {
        x: oMask.offsetWidth / 2,
        y: oMask.offsetHeight / 2,
      };

      // 计算出mask应该移动的距离
      let maskmove = {
        x: mouse.x - mask.x,
        y: mouse.y - mask.y,
      };

      // 临界值判断
      if (maskmove.x < 0) {
        maskmove.x = 0;
      } else if (maskmove.x > e.target.clientWidth - oMask.offsetWidth) {
        maskmove.x = e.target.clientWidth - oMask.offsetWidth;
      }

      if (maskmove.y < 0) {
        maskmove.y = 0;
      } else if (maskmove.y > e.target.clientHeight - oMask.offsetHeight) {
        maskmove.y = e.target.clientHeight - oMask.offsetHeight;
      }
      // 赋值，让mask移动
      oMask.style.left = maskmove.x + "px";
      oMask.style.top = maskmove.y + "px";
      // 控制大图移动
      oBigImg.style.left = -2 * maskmove.x + "px";
      oBigImg.style.top = -2 * maskmove.y + "px";
    },
  },
};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>